RUSSELL.] KECENT VOLCANOES. 57 
form tiie hills referred to was less liquid and did not flow away so 
readily, as in many other similar instances, but thickened in a more 
conspicuous manner than normally about the openings from which it 
came. 
In the formation or lava cones, as is the case with the flow of lava 
streams generally, an important condition, and the one which makes 
it possible for a small hill to form with a sheet of lava extending com- 
pletely over its summit, is the subsurface flow of liquid or plastic lava 
beneath a stiff crust. The degree to which lava escapes in this man- 
ner from a deep accumulation determines the extent to which its sur- 
face will be fractured and the amount of surface change which will 
result from tne subsidence of fragments of the crust. 
BOWDEN CRATER. 
Situated in the south-central part of Malheur County, Oregon, and 
about 6 miles northeast of the former post-office of Bowden, there is 
an isolated volcanic crater surrounded by an extensive lava flow, 
which it is convenient to designate the Bowden Crater. 
The region about Bowden Crater is composed largely of Tertiary 
lacustral deposits, and was deeply eroded before the eruption which 
built the crater. The region, in fact, had all of its present erosion 
features at the time referred to, and has been but slightly modified 
since the volcano ceased to be active. 
Bowden Crater and the lava flow about it are composed of basalt. 
There is, so far as observed, a complete absence of the products of 
explosive eruptions, such as lapilli, volcanic bombs, etc. The crater 
rises 600 feet by aneroid measure above the plain at the margin 
of its lava flow, but the lava flow and crater merge with each other, 
and the rise from the outer margin of the lava to the base of 
the cone in the center of the broad, black, desolate tract of fresh rock 
is exceedingly gradual. The upward slope for the first 3 or 4 miles 
is less than 1°; then for about 2 miles it gradually increases to per- 
haps 2° or 3°, and on the sides of the central and circular elevation 
becomes about 10°. The height of the central elevation above the 
surrounding lava is approximately 200 feet. The walls of the crater 
are of lava of the same general character as that forming the exten- 
sive sheet about it, but is perhaps somewhat more scoriaceous. The 
raised rim of the central elevation inclosed a steep-sided circular 
basin, 600 feet in diameter and about 40 feet deep. The bottom of 
the depression is level floored and consists of fine light-colored silt, 
most probably of eolian deposition. During the wet season this 
depression is converted into a shallow lake, which evaporates to dry- 
ness in summer. 
When standing on the summit of Bowden Crater no other similar 
elevation is in sight, and no other volcanic vent has as yet been dis- 
covered nearer than the Jordan Craters, situated about 30 miles to 
